Gay-rights advocate Sir Ian McKellen has spoken of his wish to marry in Wellington.

In a video made for a Wellington conference, The Hobbit star praised New Zealand for the "exciting prospect" of finally legalising same-sex marriage. Parliament is considering a bill which would clear the way for it.

"My support is with you and I hope that by the time I return to Middle-earth I might even be able to get married there," said the British star, who plays Gandalf in The Hobbit.

With a "thumbs up" signal, he added: "Good luck".

Sir Ian, 73, has spent long periods in New Zealand during filming The Lord of the Rings and The Hobbit movies.

However, he missed this week's premiere and there was speculation it was in protest at comments made by Prime Minister John Key about a radio host's "gay red shirt".

In his blog, he told Mr Key to "watch his language".

In the clip, filmed on the set of British television series Loose Women, he said the world looked to New Zealand, the first country to give women the vote, for "social advancement".

"It will be a popular move, I know, and I'm glad your major political parties have embraced it, supported too by the younger generation who see things a lot more clearly than people of my age."

The video was screened at a panel discussion at Parliament last night, hosted by the Green Party.

MP Kevin Hague said he would not be surprised if Sir Ian chose to marry in the capital.

"Sir Ian has been involved for a long time in gay right issues . . . this conference gives him the chance to say something powerful in a country that he obviously cares a great deal about and has spent a lot of time in."

Mr Hague was joined at the Legalise Love conference by colleague Jan Logie and Labour MP Louisa Wall, who sponsored the Marriage (Definition of Marriage) Amendment Bill. It has attracted more than 20,000 submissions and is being considered by a select committee.